• Authors:
    • García-Jiménez, J.
    • Botella-Rocamora, P.
    • Vicent, A.
    • Bascón, J.
    • de la Roca, E.
    • López-Quílez, A.
  • Source: European Journal of Plant Pathology
  • Volume: 133
  • Issue: 3
  • Year: 2012
  • Summary: Phytophthora branch canker, caused by Phytophthora citrophthora, has been an increasing problem in clementine ( Citrus reticulata) production in Spain during last years. The disease was particularly severe in the new citrus-growing areas of the southwestern coastal areas in Huelva Province. Recent studies revealed that disease emergence was not related to either genetic drift or host specificity changes in P. citrophthora population. Therefore, the possible association of agronomic factors with the disease was investigated. A total of 110 orchards were selected arbitrarily from the main citrus-growing areas in Huelva Province. The presence of branch cankers together with agronomic factors including soils, cultivars, rootstocks, irrigation, pruning, techniques to improve fruit production, fungicide treatments, presence of brown rot of fruit and frost damage were recorded. Logistic regression analysis was used to detect correlations between the agronomic factors studied and disease prevalence. Phytophthora branch canker was significantly associated with mature clementine orchards. Sweet orange and hybrid cultivars as well as young clementine orchards were less affected by the disease. Although disease was less frequent in Salorthid soils, alternative high resolution procedures are required to draw conclusions about the effect of soil properties on disease prevalence. As in other Phytophthora-induced diseases, soil flooding during the rainy season was correlated positively with the prevalence of branch cankers. Improving fruit production by branch scoring showed a strong positive correlation with Phytophthora branch canker. This is the first time that girdling has been associated with Phytophthora disease epidemics on a fruit tree crop, but further research is needed to determine the cause of this relationship. Cultural practices including pruning, regulated deficit irrigation, additional phosphonate sprays, and abiotic and disease factors such as frost damage and presence of brown rot of fruit were not significantly correlated with disease prevalence.
  • Authors:
    • Shu, B.
    • Zhang, J. J.
    • Wang, P.
    • Xia, R. X.
  • Source: Plant, Soil and Environment
  • Volume: 58
  • Issue: 7
  • Year: 2012
  • Summary: Communities of arbuscular mycorrhizal fungi (AMF) were studied in sod culture (SC), straw mulching (NM), and herbicide treated and no-tillage (NH) citrus orchards, respectively. The highest total colonization rate (39.47%) and hyphal length density (1.15 m/g soil) were found in SC, the highest spore numbers (1024 spores/100 g soil) in NM, while the lowest ones (31.50%, 0.94 m/g soil and 719 spores/100 g soil) in NH and they varied significantly among three different types of orchards. Total 18 AMF species belonging to five families, Acaulosporaceae (four species), Claroideoglomeraceae (two species), Gigasporaceae (one species), Glomeraceae (nine species) and Pacisporaceae (two species) were identified, and Glomus aggregatum and Claroideoglomus etunicatum were the dominant species in all surveyed plots. The redundancy analysis showed that AMF community structure was influenced greatly by pH, soil management, soil organic matter (C ox) and available phosphorus (P Olsen). In SC orchards, species richness and Shannon-Wiener index of AMF were notably higher than in other treated orchards. So, it is reasonable to select SC as the best practice in citrus orchard in order to enhance AMF benefits.
  • Authors:
    • Hulugalle, N. R.
    • Ghadiri, H.
    • Weaver, T. B.
    • Harden, S.
  • Source: Chemosphere
  • Volume: 88
  • Issue: 3
  • Year: 2012
  • Summary: Organochlorine pesticides (OCPs) such as DDT and DDE have been detected in the surface 0.2 m of Vertisols in the lower Namoi Valley of north western New South Wales, Australia even though they have not been applied to crops since 1982. However, their presence in the deeper soil horizons has not been investigated. The objective of this study was to determine if OCPs were present to a depth of 1.2 m in Vertisols under irrigated cotton farming systems in the lower Namoi Valley of New South Wales. Soil was sampled from the 0-1.2 m depths in three sites, viz. the Australian Cotton Research Institute, ACRI, near Narrabri (149 degrees 36'E, 30 degrees 12'S), and two cotton farms near Wee Waa (149 degrees 27'E, 30 degrees 13'S) and Merah North (149 degrees 18'E, 30 degrees 12'S) in northern New South Wales, Australia. The OCPs detected and their metabolites were alpha-endo-sulfan, beta-endosulfan, endosulfan sulphate, DDD, DDE, DDT and endrin. The metabolite DDE, a breakdown product of DDT, was the most persistent OCP in all depths analysed. Endosulfan sulphate was the second most persistent followed by endrin > alpha-endosulfan > beta-endosulfan > DDT and DDD. DDT was sprayed extensively in the lower Namoi Valley up to the early 1980s and may explain the persistence of DDE in the majority of soil samples. Dicofol and Dieldrin. two OCPs previously undocumented in Vertisols were also detected. The movement of OCPs into the subsoil of Vertisols may occur when irrigation or rain transports soil colloids and organic matter via preferential flow systems into the deeper layers of a soil profile. Persistence of OCPs was closely correlated to soil organic carbon concentrations. The persistence in soil of OCP's applied to cotton crops grown more than two decades ago suggests that they could enter the food chain. Their presence at depths of 1.2 m suggests that they could move into groundwater that may eventually be used for domestic and stock consumption. Crown Copyright (C) 2012 Published by Elsevier Ltd. All rights reserved.
  • Authors:
    • Ma, C. L.
    • Wang, P.
    • Guo, P.
    • Peng, H. Y.
    • Chen, L .S.
    • Yang, L. T.
  • Source: Scientia Horticulturae
  • Volume: 133
  • Year: 2012
  • Summary: 'Sour pummelo' ( Citrus grandis) seedlings were irrigated for 18 weeks with nutrient solution containing 0 (-Al) and 1.2 mM (+Al) AlCl 3.6H 2O * 0, 10 and 500 M sodium nitroprusside (SNP), a nitric oxide (NO) donor. Leaf malate content did not significantly change in response to SNP with or without aluminum (Al) except for an increase under 1.2 mM Al+10 M SNP, while leaf citrate content decreased with increasing SNP supply. Root malate content kept unchanging with or without Al except for an increase under 500 M SNP in the absence of Al, while SNP-treated roots had a higher or similar citrate content. Al decreased or did not affect malate content in roots and leaves, and citrate content in roots, but increased leaf citrate content. Al-treated roots and leaves displayed lower or similar activities of acid-metabolizing enzymes [phospho enolpyruvate carboxylase (PEPC), NAD-malate dehydrogenase (NAD-MDH), NADP-malic enzyme (NADP-ME), citrate synthase (CS), aconitase (ACO), NADP-isocitrate dehydrogenase (NADP-IDH), phospho enolpyruvate phosphatase (PEPP) and pyruvate kinase (PK)] except that they had higher or similar activities of NADP-ME and PK and Al-treated leaves had a higher or similar activity of PEPP. In conclusion, the OA metabolism in leaves and roots is differently affected by NO and Al interactions.
  • Authors:
    • Chachalis, D.
    • Mavromatis, A.
    • Khah, E. M.
    • Kostoula, S.
    • Zaxos, D.
    • Sakellariou, M.
  • Source: International Journal of Plant Production
  • Volume: 6
  • Issue: 1
  • Year: 2012
  • Summary: The effect of row spacings and irrigation levels on the earliness of seed production of cotton was investigated under the Mediterranean environment of central Greece. This particular cotton growing area is exposed to risk of autumn rainfall that might cause low seed quality in fields allocated primarily for seed production. Two varieties of cotton, Celia and Hersi, were planted in two row spacings (93 and 75 cm) and two irrigation levels (normal and low levels 6160 and 3080 mm ha(-1)). No significant difference in the yield was found among the two varieties, nor between the two row spacings. The low irrigation level had significantly negative effects on the number of squares, bolls, total dry weight and seed cotton production when compared with irrigation level. However, the low irrigation level resulted in a harvest earlier by ten days, which contributed to avoiding autumn rainfall. Seed quality (measured by germination and Warm-Cold Vigour Index Test) was better in seeds from the low irrigation level than in those from the normal irrigation level. Although yield of both varieties was higher under normal irrigation, seed quality was lower compared to low irrigation level. This was evidenced by the higher Free Fatty Acid (FFA) in "normally" irrigated plants. The results of this study showed that low irrigation level offers substantial benefits for early harvesting and production of high seed quality. Moreover, the FFA could be successfully employed as a quick criterion for seed quality ranking.
  • Authors:
    • Desneux, N.
    • Han, P.
    • Niu, C. Y.
    • Zhou, X. W.
  • Source: Journal of Economic Entomology
  • Volume: 105
  • Issue: 4
  • Year: 2012
  • Summary: The Chinese citrus fruit fly, Bactrocera minax (Enderlein) is a univoltine Tephritidae pest that infests Citrus species. Field trials were conducted in 2010 to determine the potential use of a lure based on enzymatical-hydrolyzed beer yeast as liquid bait (hereafter named H-protein bait) for B. minax in the Hubei province, China. In a citrus orchard, we compared the attractiveness among aqueous solutions of H-protein bait, GF-120 fruit fly bait, sugar-vinegar-wine mixture, torula yeast, and Jufeng attractant when used in traps and in spot sprays, that is, lures used in combination with the insecticide trichlorphon. The H-protein bait was the most attractive lure in traps, ensnaring significantly more adults than sugar-vinegar-wine mixture, torula yeast, and Jufeng attractant, in decreasing efficiency order. In spot sprays those with H-protein bait killed significantly more female and male flies within 40 min than those with sugar-vinegar-wine mixture, GF-120, Jufeng attractant, and the control. In addition, the total number of flies killed by H-protein bait during the spot spray duration was higher than other treatments. Our results demonstrated that the H-protein bait may be a useful tool in citrus orchards in China to monitor B. minax populations as well as to manage this pest when used in spot sprays.
  • Authors:
    • Mulas, M.
    • Deidda, B.
    • Zurru, R.
  • Source: Acta Horticulturae
  • Issue: 928
  • Year: 2012
  • Summary: Pruning of Clementine requires a lot of time: more than 50 days of work per hectare in the traditional forms of orchard management. Because of the high cost and the lack of specialised workers, we observe a general tendency to delay the frequency of pruning in the citrus orchards. On the other hand regular pruning is of fundamental importance to have good fruit quality, to maintain health status of the orchard, and to store their regular productivity. In order to optimise the Clementine pruning technique, reduce the time of execution and maintain a good level of yield of better quality a field experiment was designed. In 1996 a commercial orchard of 'SRA 63' Clementine located in Southern East Sardinia was selected for the experiment. Plants were grafted on 'Troyer' Citrange, twenty-year-old, spaced 7*5 m, shaped to globe, over 4 m in height, and showed an excessive number of main branches (about 7-8 per tree) with a dense canopy. The entire orchard was preliminarily submitted to a gradual shape pruning during the first four years. In 2000 two main plots of 72 plants each were designed: (A) pruning every year; and (B) pruning every two years. The orchard was observed for a further period of four years for the following characters: trunk section area; canopy size, working time for pruning; pruned wood weight; fruit yield; fruit size. In both pruning applications (A and B) the canopy was more open and green than in the past, with a improvement of the plant heath status, a reduction of the number of treatments, water for irrigation and fertilizers, less working time for harvest, and with a significant better fruit size and increase of the production value.
  • Authors:
    • Coquet, Y.
    • Justes, E.
    • Benoit, P.
    • Alletto, L.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 153
  • Year: 2012
  • Summary: Water drainage and herbicide degradation and leaching were studied during four years in a continuous maize field managed with two tillage systems and two types of fallow periods. The tillage systems consisted of either a conventional practice with mouldboard ploughing (28 cm-depth) or a conservation practice with superficial tillage (
  • Authors:
    • Vogt, G. A.
    • da Veiga, M.
    • Balbinot Junior, A. A.
    • Spagnollo, E.
  • Source: Ciência Rural
  • Volume: 42
  • Issue: 3
  • Year: 2012
  • Summary: The objective of this study was to evaluate in the fifth year of experimentation, the effect of winter soil uses on residual straw on the soil, physical and chemical soil attributes and grain yield of common bean cultivated in succession. An experiment was carried out in the North Plateau of Santa Catarina State, Brazil, from May 2006 to April 2011. Five winter soil uses were investigated: 1) multicropping with black oat + ryegrass + common vetch without grazing (multicropping cover); 2) the same multicropping, with grazing and 100kg ha(-1) of nitrogen year(-1), applied during the growing period (pasture with N); 3) the same multicropping, with grazing and without nitrogen fertilization (pasture without N); 4) oil seed radish, without grazing (oil seed radish); and 5) natural vegetation, without grazing (fallow). In the fifth year of experimentation, multicropping cover treatment inputted greater straw on the soil, but it was not observed expressive differences in soil attributes among the five winter soil uses. Cover crops, annual pasture and winter fallow did not affect the grain yield of common bean cultivated in succession.
  • Authors:
    • Pitelli, R. A.
    • Bianco, M. S.
    • Carvalho, L. B.
    • Bianco, S.
  • Source: Planta Daninha
  • Volume: 30
  • Issue: 1
  • Year: 2012
  • Summary: Soybean is one of the main crops in Brazil, but its productivity is very affected by weed competition. Two experiments were carried out in Jaboticabal, SP, Brazil, under greenhouse conditions to determine the accumulation and distribution of dry mass and macronutrients in soybean cv. BR-16, from October 2000 to February 2001, and Solanum americanum plants, from January to May 1995. Plants were grown in seven liter pots filled with river sand substrate and were daily irrigated with nutrient solution. The treatments were constituted by the times of samplings carried out at 14 day intervals, starting 21 days after emergence (DAE). Soybean evaluation was extended to 161 DAE, while S. americanum was extended to 119 DAE. The point of maximum theoretical accumulation of dry mass in soybean occurred at 104 DAE (35.00 g per plant) while for S. americanum, it occurred at 143 DAE (179.62 g per plant). From emergence until 49 and 63 DAE, leaves showed higher participation in dry mass accumulation of soybean and S. americanum, respectively. After these periods, an inversion could be observed, with leaves being surpassed by stems for the weeds, and by stems and later, by reproductive structures, for the crop. Macronutrient uptake rate reached higher values between 69 to 87 DAE for soybean and between 105 to 119 DAE for S. americanum. Considering the mean inflexion point values observed in soybean crop, at 75 DAE, it can be evidenced that one soybean plant theoretically accumulated 23.90 g of dry mass, 564.40 mg of N, 7.10 mg of P, 490.80 mg of K, 487.00 mg of Ca, 156.60 mg of Mg and 36.00 mg of S, while one S. americanum plant theoretically accumulated 33.75 g of dry mass, 875.96 mg of N, 88.46 mg of P, 983.54 mg of K, 647.60 mg of Ca, 100.93 mg of Mg, and 42.15 mg of S.